Combine the spinach leaves, basil leaves, and the chilled vegetable stock, and purée in a blender until smooth.

Then add the heavy cream, and season with salt and pepper to taste. Purée the mixture again until smooth, strain the liquid to ensure there are no lumps, and pour it into a siphon bottle.

Insert one nitrous oxide cartridge into the siphon and shake it vigorously.

Let it chill for 1-2 hours, and then it is ready to be placed on top of your smoothie.

The celery should be washed, peeled, and cut into small cubes. Then wash and dry the parsley. Purée both with water, using either an immersion blender or a regular blender until smooth.

Next, add the grapefruit juice and apple juice, purée again until smooth, and pour it into a glass.